The present invention relates generally to circuit condition monitoring devices for use in electrical power distribution systems, and in particular to a clamp mechanism for clamping such devices to the cables of such distribution systems.
Electrical power distribution systems may require the use of a variety of circuit condition monitoring devices to facilitate the detection and location of system malfunctions. Such devices include manually and automatically reset current fault indicators, such as those manufactured by E. O. Schweitzer Manufacturing Co., and described in U.S. Pat. Nos. 4,288,743, 4,086,529 and 3,676,740 of the present inventor, as well as voltage monitoring devices, such as described in U.S. Pat. Nos. 4,251,770, 4,152,643, 4,263,350 and in U.S. patent application No. 518,536, filed July 29, 1983, now U.S. Pat. No. 4,550,288, of the present inventor. The devices may be either of the test point mounted type for mounting on a system test point, or of the clamp-on type, for clamping directly onto a cable of the system.
Clamp-on type devices typically include a housing containing monitoring circuitry, a circuit condition indicator, and some form of clamp mechanism affixed to the housing for mounting the housing on a cable. Frequently, the clamp mechanism serves the additional function of establishing either magnetic or electrostatic communication, or both, between the cabler and appropriate sensing components of the monitoring apparatus.
Clamp mechanisms of the type previously known in the art for mounting distribution system monitoring devices typically required the use of both hands as well as a pair of live-line handling tools during installation on a system cable. Consequently, such clamp mechanisms were undesirably difficult and time consuming to install, and provided an undesirable risk of electric shock as a result of the additional manipulation required.
In one prior clamp mechanism, which is described in U.S. patent application No. 289,916, filed Aug. 4, 1981, now U.S. Pat. No. 4,456,873, of the present inventor, a plurality of flexible metallic strips are combined to form a generally square-shaped magnetic core for use with a circuit condition monitoring device. One end of the core is affixed to the device housing, and the opposite end is detachably received within an aperture in the housing opposite the first end. In use, the free end of the core is displaced from the device housing, allowing the core to be passed around a cable. The free end is then inserted in the aperture to lock the device to the cable. A similiar core structure is shown in U.S. Pat. No. 3,725,832 of the present inventor.
In another prior clamp mechanism, which is described in U.S. Pat. No. 4,288,743, two insulated metallic members project from the rear surface of the device. A third spring-biased member normally occupies a position engaging the two projecting members, but can be displaced from the members to allow a cable to be introduced between the two members. The spring-biased member is then allowed to return to its normal position to clamp the device to the cable.
The present invention is directed to a clamping mechanism for automatically clamping a monitoring device to an electrical cable such as utilized in an electrical distribution system. In particular, the invention is directed to a clamp mechanism which is automatically actuated closed when the mechanism is brought into contact with a cable, thereby allowing a lineman to install the monitoring device with the use of only one hand. Considerable time is saved through use of such a mechanism, and the resulting one-hand installation contributes to safety, particularly where it is necessary for the lineman to ascend a ladder in order to install the device, or where the monitored cable is closely spaced to other cables and can only be approached from one direction.
Accordingly, it is a general object of the present invention to provide a new and improved clamp mechanism for circuit monitoring devices.
It is a more specific object of the present invention to provide a clamp mechanism for clamping a circuit condition monitoring device to the cable of a power distribution system which requires the use of only one hand during installation.
It is a further object of the invention to provide a clamp mechanism for a cable-mounted closed-core condition monitoring device wherein the core is actuable to an open condition for receiving the cable, and is automatically actuated to a closed condition upon engaging the cable.